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IT17058: SIGSEGV in xtrWriteTraceHeader if MQ trace is on, and getpwuid call fails

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You can track all active APARs for this component.

 

APAR status

  • Closed as program error.

Error description

  • MQ called getpwuid to find a username to write in the header at
    the top of an MQ trace file.
    
    Something was wrong in the user/group subsystem causing the
    getpwuid call to fail even though the uid being queried had been
    returned from geteuid a moment beforehand.
    
    Immediately after the failed getpwuid call, the MQ code used a
    null pointer, which caused a SIGSEGV, which caused a core file
    from the user's process, and the ending of the process.
    
    The underlying root cause of such a problem is external to MQ.
    
    But MQ should not cause a memory exception when it happens.
    
    In addition, some separate errors may be seen written in FDC
    files from other parts of MQ with the same underlying reason
    within the user/group database.
    Example:
    PROBE ID:  XY051170
    Comment1 :- xcsGetpwuid failed to get password entry for process
    Comment2 :- Details: getuid() returned 41668358;
    getpwuid_r(41668358) failed with errno=0.
    Comment3 :- A user name of "UNKNOWN" will be used, which will
    likely cause later authorisation failures. Note this FFST can be
     turned off by exporting env var AMQ_NOFFST_PROCESS_UID.
    

Local fix

Problem summary

  • ****************************************************************
    USERS AFFECTED:
    Users who are switching on MQ trace, and have a serious problem
    in their user/group database causing getpwuid to fail for a uid
    that the OS has just returned via getuid or geteuid.  This
    problem has only been seen on a system where the user/group
    database was managed externally from the local operating system.
    
    
    Platforms affected:
    AIX, HP-UX Itanium, Linux on Power, Linux on x86, Linux on
    x86-64, Linux on zSeries, Solaris SPARC, Solaris x86-64
    
    ****************************************************************
    PROBLEM DESCRIPTION:
    The root cause of such a problem is external to MQ.  But MQ
    should not have caused a memory exception when it happens, this
    was due to an incorrect pointer access within MQ when handling
    the external error.
    

Problem conclusion

  • The MQ product code has been changed to ensure that a null
    pointer is not used in this failure scenario.
    
    ---------------------------------------------------------------
    The fix is targeted for delivery in the following PTFs:
    
    Version    Maintenance Level
    v8.0       8.0.0.6
    v9.0 CD    9.0.4
    v9.0 LTS   9.0.0.1
    
    The latest available maintenance can be obtained from
    'WebSphere MQ Recommended Fixes'
    http://www-1.ibm.com/support/docview.wss?rs=171&uid=swg27006037
    
    If the maintenance level is not yet available information on
    its planned availability can be found in 'WebSphere MQ
    Planned Maintenance Release Dates'
    http://www-1.ibm.com/support/docview.wss?rs=171&uid=swg27006309
    ---------------------------------------------------------------
    

Temporary fix

Comments

APAR Information

  • APAR number

    IT17058

  • Reported component name

    WMQ BASE MULTIP

  • Reported component ID

    5724H7251

  • Reported release

    800

  • Status

    CLOSED PER

  • PE

    NoPE

  • HIPER

    NoHIPER

  • Special Attention

    NoSpecatt / Xsystem

  • Submitted date

    2016-09-15

  • Closed date

    2016-09-22

  • Last modified date

    2017-06-09

  • APAR is sysrouted FROM one or more of the following:

  • APAR is sysrouted TO one or more of the following:

Fix information

  • Fixed component name

    WMQ BASE MULTIP

  • Fixed component ID

    5724H7251

Applicable component levels

  • R800 PSY

       UP

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Document Information

Modified date:
09 June 2017